Characteristics of T-cell immunity and level of the natural killer cells content in COVID-19 convalescents with carbohydrate metabolism disorders

The pandemic of the new COVID-19 coronavirus infection has created a public health emergency in the Russian Federation in 2020-2022. COVID-19 causes various consequences, often manifested by the endocrine system dysfunction. The rationale for our study is insufficient data on T and NK cell immunity in patients with hyperglycemia after COVID-19. The study was aimed at the features of T cell immunity in individuals with post-COVID syndrome and disorders of carbohydrate metabolism, depending on the NK cells count. Materials and methods: Sixty-four post-COVID patients with carbohydrate metabolism disorders were divided into three groups: with reduced, normal, or elevated NK cell counts. Carbohydrate metabolism disorders included impaired glucose tolerance (n = 36) and type 2 diabetes mellitus (n = 28). The comparison group comprised 60 post-COVID persons with no history of carbohydrate metabolism disorders. The assessment of the lymphocytic link of immunity included the definition of: CD45⁺CD3⁺ (T lymphocytes), CD45⁺CD3⁺CD4⁺ (T helpers), CD45⁺CD3⁺CD8⁺ (T cytotoxic), CD45⁺CD3⁺CD16⁺CD56⁺ (T-NK cells), CD45⁺CD3^-CD16⁺CD56⁺ (natural killers), CD45⁺CD3⁺CD4⁺CD25⁺ (T lymphocytes – early activation), CD45⁺CD3⁺HLA-DR⁺ (T lymphocytes – late activation). Results and Discussion. As the study showed, a decrease in the number of natural killers was accompanied by a higher level of T helpers in the group with carbohydrate metabolism disorders, the latter is probably associated with a compensatory increase in T lymphocytes and dysregulation of the T cell link of the immune system. It can also be concluded that in patients with long-COVID and CMD, with normal NK cell counts, an altered subpopulation composition remains, namely, a significant increase in total T lymphocytes. Many authors associate the obtained data on a significant decrease in T-NK lymphocytes with a decrease in the antiviral activity of the immune system, which can lead to a poor response to new viral agents or contribute to the activation of chronic viral infections. Dysregulation of the T cell link in individuals with long-COVID and disorders of carbohydrate metabolism requires a more detailed study, including an assessment of the cytokine profile in this category of patients.

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